German Patent Publication DE 4,443,371 C1 corresponding to U.S. Pat. No. 5,606,998 (Wahhoud et al.) discloses a weft detecting and stretching apparatus for a jet weaving loom, wherein the weft insertion channel in the reed can be lengthened or shortened at the exit end of the insertion channel by telescoping or extension sections forming one or more channel extension members. At least one weft stop motion device for sensing a weft thread extending out of the extension channel is provided for the extension channel. If two channel extensions are provided, one for weft guiding and one for weft stretching, then it is necessary according to U.S. Pat. No. 5,606,998 to provide a separate weft stop motion device for each of the two extension channels.
One of the channel extensions forming a weft guide is axially aligned with the weft insertion channel while the weft stretching channel extension preferably runs in parallel to the weft guide channel extension. Each channel extension is provided with its own weft stop motion device.
U.S. Pat. No. 5,226,458 (Bamelis) discloses a weft thread stretching mechanism or weft stretcher arranged at the exit end of the weft insertion channel through the reed. The weft stretcher and the reed are connected to the sley of the loom. The loom operates with a pneumatic weft insertion. The weft stretcher of Bamelis includes a weft thread guide channel positioned downstream of the weft thread exit area from the weft insertion channel in the reed as viewed in the weft insertion direction. The weft guide channel is aligned with the weft insertion channel in the reed. At the inlet of the stretching device, two openings are provided opposite one another. These openings form an exit of a first flow air channel and an inlet of a second air flow channel into which a weft thread leading end is diverted for the stretching by an airstream flowing out of the first flow channel into the second flow channel across the longitudinal central axis or plane of arrangement of the weft guide channel. The second stretching flow channel also forms a weft guide channel in the stretching device. Bamelis does not disclose any weft stop motion devices for his two channel extensions.
International Patent Publication WO 97/13017 (Bamelis et al.) discloses a weft stretching device attached to the exit end of the weft insertion channel in a reed. The stretching device has but one channel especially provided with weft diverting elements for guiding the weft thread along a weft stretching path. The weft diverting elements are positioned for stretching the weft thread, whereby a specially shaped single channel performs the functions of two channels. This International Publication WO 97/13017 does not disclose any weft stop motion devices.
The above described prior art leaves room for improvement. Where a single channel is equipped with weft guide elements, the consistent stretching of each weft thread is not always assured because the leading end of the weft thread being inserted may miss the critical guide element and thus stretching does not take place or at least proper stretching does not take place. On the other hand, where a guide channel and a stretching channel are arranged in parallel to each other at the exit end of the weft insertion channel in the reed, the space available for the positioning of the device may not be sufficient, especially if each channel is provided with its own weft stop motion device as is conventional.